Field of the Invention
The invention relates to a method for stabilizing a rear-wall structure in a seat structure, and a seat structure, producible by the method, with selectively determined laser-strengthened regions in the area of a rear wall.
Description of the Background Art
DE 10 2007 024 797 A1, which corresponds to U.S. Pat. No. 8,272,681, discloses a method for producing a profile component from a semifinished sheet metal part, which has a structurally increased strength at least in sections. The semifinished sheet metal part is formed in an at least single-stage bending process. The bending process with the subsequent separating and cutting operations on the semifinished sheet metal part is combined with a thermal treatment of the at least one spatially delimited region of the semifinished sheet metal part. The thermal treatment comprises at least one heating step and one cooling step following it. The at least one spatially delimited region has a structurally increased strength after cooling. Profile components with an open, with a partially open, or also with a completely closed profile cross section and with hardness properties adapted in a directed manner can be produced by the process. It is possible to produce a profile component, which in sections has hardened regions and in sections non-hardened regions. The hardened regions can be partially hardened, completely hardened, or also partially hardened in sections and completely hardened in sections. For example, the forming of the profile component in DE 10 2007 024 797 A1 occurs by roll profiling and the heating of locally defined regions for strengthening these regions occurs before, during, or after the forming.
The local spatial heating of the semifinished sheet metal part can be achieved advantageously by the inductive generation of an electromagnetic field or by a conductive current flow by means of the electrical resistance (or by a combination of these two processes), therefore, by dissipation of electrical energy. In other embodiments, there is also the possibility that the heat is introduced into defined regions of the semifinished sheet metal part by one or more laser light sources, by an infrared radiation source, or by means of a gas burner. Laser light sources have the advantage that the laser light generated by them can be focused, for example, by simple means also on a relatively small spatially delimited region of the semifinished sheet metal part to bring about local heating to the desired temperature in this region.
In the so-called laser strengthening, in which regions, hardened at least in sections, in the profile component can be created, a carbon steel is heated for short time above the austenitizing temperature and converted by rapid cooling to the harder martensitic microstructure. In this regard, the heat is produced via the absorption of the laser radiation on the surface. The quenching occurs by heat conduction into the material interior. The hardening depth in laser strengthening is limited by the heat transport and self-quenching. The temporal temperature profile is determined substantially by the spot geometry of the laser beam at the machining site and the rate of advance of the laser beam relative to material. Laser sources often used in welding and laser strengthening are primarily the CO2 and Nd:YAG laser, whereby the rapidly evolving fiber lasers are currently also gaining increasing acceptance in different technical fields.
DE 10 2011 101 700 A1 describes the use of laser strengthening for selectively influencing the deformation behavior of a seat part structure. The aim is to prevent the buckling and breaking of the seat structure in greatly stressed regions of a backrest adjuster particularly in the event of a crash. This is to be achieved by introducing short laser-welded seams in this region. The laser-welded seams by means of the above-described process cause an increase in strength locally in the introduced regions.
It is known that larger components, such as metal sheets, are in a metastable state because of the manufacturing process. The effect known as the “clicker” effect indicates that another stable or metastable state can be assumed with a relatively low force application to the component. The effect often accompanied by a noise indicates tensions in the component. These tensions disadvantageously induce instabilities in the component.
The “clicker effect” occurs particularly in flat components whose width and/or length are considerably greater than their wall thickness, particularly in the case of the mentioned metal sheets. It is also known to occur when metal sheets are used in car body construction and when metal sheets are used in seat structures.
To increase the stability of seat structures, known methods focus on wall thickenings to reduce the motion tolerance of the seat structure.
A drawback of these methods, nevertheless, is that they are cost-intensive and lead to an increased weight of the component modified in this way.
Another approach is the embossing of so-called ribbed structures. The ribbed structures stabilize a flat component without increasing the weight of the component.